Gas turbines and comparable fluid-flow machines as a rule comprise axial compressors in order to make available a compressed-air flow for a combustion process. Compared with other compressor types, axial compressors are characterized by a high efficiency, wherein on the pressure side of the compressor, high pressures can be achieved when the axial compressor has a sufficient multiplicity of compressor stages. However, the design effort when increasing the number of compressor stages increases greatly. The aim therefore is to make possible a high pressure on the pressure side of the compressor even with a comparatively low number of stages. This is synonymous to each compressor stage having to be able to generate or maintain a comparatively large pressure differential between suction and pressure side of the respective compressor stage. With today's axial compressors, this is guaranteed with high reliability.
At the same time it remains difficult to guarantee a stable operating behaviour under changing operating conditions. There is always the risk of a compressor stall, particularly on the suction side of the rotor blades. In such an event, the mass flow of the fluid to be compressed generated by the axial compressor suddenly drops, wherein in the worst case even a back stroke of the fluid to be compressed can occur.
For this reason, a large stability range of the compressor stages is regularly aimed at when designing an axial compressor.